The present invention is directed generally to a time-temperature indicator device for indicating a specified number of time-temperature events such as sterilizations of a medical instrument. The invention is directed, more specifically, to a device for indicating a specified number of uses and subsequent sterilizations of files for use in endodontic operations, i.e. root canal therapy.
In many endodontic operations, it is necessary to successively insert an elongated instrument into, and then pull the same from the root canal of a tooth in order to thoroughly remove any inflamed or necrotic tissue therein and properly enlarge the canal. The instrumented root canal is subsequently sealed off with aseptic material.
The conventional endodontic instrument which is used in the root canal treatment described above, generally consists of a thin flexible wire with an abrasive surface acting as a file, a reamer, or the like, a handle, and a stop of elastomeric material such as natural or synthetic rubber. The handle, which is adapted for gripping by the operator, is securely fixed at one end of the wire. The rubber stop, on the other hand, is movably attached to the wire and can be easily relocated therealong.
It is generally known that a human tooth consists of pulp chamber, root canal, enamel, dentin, and cementum, wherein the pulp chamber and the root canal are composed of nerve tissue and blood vessels. Therefor, when the tissue of the pulp suffers from traumatic injury, caries and periodontal infection, inflammation or necrosis of the pulp tissue will occur. Endodontic therapy, generally called "root canal treatment" is necessary to retain the tooth. The main work required for the endodontic therapy is to thoroughly remove the inflamed or necrotic pulp tissue, and then to seal up the root canal with aseptic material. In order to successfully perform the endodontic therapy, the root canal length of the involved tooth must be exactly measured before the root canal is sealed up. Accordingly, the most important work in endodontic therapy is to measure the exact root canal length of the tooth because only when debridement is performed completely in the tooth can the root canal be sealed up thereat.
Concerning the measurement of the root canal length, various methods are adopted in endodontic therapy, and one of the frequently used methods is X-ray, for which a reamer, or file, is inserted into the root canal, and then an endodontic stop, movably attached to the reamer or file, is adjusted to have its bottom surface kept in contact with the incisal edge, or the cusp tip of the tooth for being X-rayed thereat. The position of the stop at the wire determines the working length of the instrument, i.e., the length of the wire to be embedded in the tooth during the treatment, since the stop prevents further penetration of the wire into the canal in the tooth when its bottom surface bumps onto the incisal edge or cusp tip of the tooth being treated.
Historically, endodontic files and reamers have been composed of differing shapes of sinless steel wire that has been ground, or more often twisted to provide a cutting edge. More recently, nickel-titanium compounds have been used to construct these files to improve their properties and efficiencies. While much has been made of the improvement of these files, one of their biggest drawbacks is the increased incidence of breakage while in the root canal. This is not a desirable outcome, and can have serious medical and legal ramifications in that it may be the direct result of the failure of the root canal therapy being performed. Dentists and file manufacturers should want to decrease the incidence of file breakage in the canal by whatever means possible. Devices have been invented to remove obstructions such as broken instruments from root canals. However, it is always preferable to prevent the obstruction in the first place.
Statistically, the incidence of fracture of the nickel-titanium, as well as other endodontic file breakage increases with additional uses, and with repeated sterilization. No automatic method of monitoring usage or sterilization of these instruments currently exists.
These and other difficulties experienced with the use of endodontic instruments and attempts to monitor usage of the instruments have been obviated by the present invention.
It is, therefore, a principle object of the invention to provide a mechanism for monitoring usage and subsequent sterilization of endodontic instruments.
A further object of the invention is the provision of a mechanism for providing a visual indication of usage and sterilization of endodontic instruments which is relatively simple to make and easy to use.
Another object of the invention is the provision of a dental file having time-temperature indicator means of the handle of the file.